1/21 - 11pm - Severe Weather Outbreak Possible Tomorrow

A line of strong storms moved through West Tennessee this morning, but what's on the way for tomorrow evening could be even more potent with the potential for damaging winds and tornadoes. Check out my broadcast from this morning below to see what all this means and then continue on below the video for a detailed severe weather breakdown:

Timing and Threats

The Storm Prediction Center has issued a Slight Risk with a 30% hatched area for tomorrow's severe weather event from Mississippi to Indiana. The main time frame for these storms to roll through West Tennessee and Mississippi will be from 5pm tomorrow to 3am Monday. This does not mean ten straight hours of storms in any one location, but rather a ten hour window where storms will be affecting the region. Wind damage and hail will be the most common threats, but this could also be a significant tornado event. Some individual supercells or cell clusters may form ahead of a main QLCS (squall line) of storms late tomorrow afternoon and evening. These front-running storms, should they form, would be the ones with the highest tornado risk, but both the line of storms and the individual cells could produce a significant tornado or two. The SPC's wording on their Slight Risk outlook is fairly strong:

AN APPRECIABLE SEVERE EVENT IS POSSIBLE ACROSS THE REGION SUNDAY NIGHT/EARLY MONDAY...INCLUDING THE POTENTIAL FOR TORNADOES AND DAMAGING WINDS. AN UPGRADE TO A CATEGORICAL MODERATE RISK MAY BE WARRANTED IN SUBSEQUENT OUTLOOKS FOR PORTIONS OF THE REGION.

Setup

The setup for tomorrow's severe weather event is fairly classic. A large trough will be moving through the region providing increased wind speed aloft, which increases instability and provides wind shear. This trough will also be negatively tilted, meaning the axis or tightest gradient of the trough will be leaning from southeast to northwest as you see in the graphic to the right from the 0z NAM model. This negative tilting further increases wind shear because the upper level winds take on a more southerly component rather than a southwesterly one.

Not only will we have wind shear between the surface and aloft, but also the surface and the low levels of the atmosphere too. This low-level shear is essential for tornadoes to form and for storms to overcome low levels of instability. The NAM output has quite a bit of low-level shear from Mississippi all the way to Kentucky, so that's a pretty good indication that rotating storms and tornadoes will be possible during the duration of this event tomorrow.

The amount of moisture that will be surging up from the Gulf of Mexico while the region is in the warm sector of this system is going to be tremendous. The current dewpoint in Starkville, Mississippi is 41 degrees, but by tomorrow evening we'll be in the 60's. That is certainly enough moisture to supply the atmosphere with the needed instability for severe weather.

When you put together these factors plus the idea that we may have CAPE (instability) values over 1000 J/kg, you get a fairly decent tornado risk. The Significant Tornado Parameter exceeds 2 on the 21z SREF model at 9pm and midnight (1/23) tomorrow and has been fairly consistent on the last few runs of the SREF. This is not "off the charts" or anything like that, but it's enough to raise eyebrows. As stated above, both individual cells and the main QLCS line of storms could produce strong tornadoes. The QLCS will be especially difficult because there could be embedded supercell structures within it that produce tornadoes like an individual supercell would. I still think the highest tornado risk will be in Northeast Mississippi (Starkville, West Point, Columbus, Tupelo, Corinth, etc.), but the latest indications like the STP above are pointing toward that threat leaking over into southern portions West Tennessee as well.

I'll be updating my Twitter, Facebook, and Google+ accounts all day tomorrow as these storms roll through, so be sure to follow or friend me for the latest information.

11/28 - 2:45pm - An Early Shot of Winter Weather

A complicated upper-level low is making for some difficult forecasting over the next 24 hours as it brings the first real chance of snow to the South this season. This upper-level low is basically a big bubble of cold air aloft that has been orphaned from a bigger system that has since moved away from the region. Since we still have showers in the area, this cold air will help to turn those into snow by late tonight in areas near Starkville and northward. Since temperatures at the surface here in Starkville won't make it above 34 or so, any brief period of snow we see will not stick to the ground. I do think there could be a complete changeover to snow here in Starkville tomorrow morning around 8 or 9am, but this is highly dependent upon how well the computer models handle this system. Further north near Tupelo, Memphis, and Jackson, TN there will be enough cold air to get the snow on the ground when it falls, but the vast amount of warm rain we've had lately has kept the ground warm and moist, so snow accumulations won't stick around for long. Travel hazards won't be a huge deal since the roads are still warm, but it's a good idea to keep a look out for slick spots where temperatures dip below freezing tonight. Click on the SREF model snow output to the right... I think it has the most reasonable estimate on who will get accumulating snow tonight.

A Winter Storm Watch has been issued for areas from Tupelo to McNairy County, TN until 6am tomorrow since heavier snow could result in accumulations of 3 inches or more. The Winter Weather Advisory around the periphery of the Watch is for wet snow accumulations that could total around 1 to 3 inches. The snow should end by late morning tomorrow as it converts back to rain showers and then the precipitation will clear the area completely by around noon or so.

Check out my video below for a complete look at this week's forecast in Starkville and more details about the snow that's headed our way:

This evening at 6pm is the annual Starkville Christmas Parade. I'll be doing a short weather segment for the parade broadcast on WOBV 5 in Starkville. This event will also be streamed live on the web, so be sure to check out http://parade.wobv5.com/ tonight at 6pm CST to see my forecast and enjoy the parade!

4/14 - 7pm - MS/TN/AL Tornado Outbreak Possible Tomorrow

Severe Weather Setup

A potential tornado outbreak is poised to affect Mississippi, Alabama, and Tennessee tomorrow as a rather potent low and associated trough swing through the central part of the nation. Once a warm front passes through the region tomorrow morning and moisture from the south begins to filter in, all forms of severe weather will be possible in North Mississippi, North Alabama, and West Tennessee. I want to place a particular emphasis on Northeast Mississippi and Northwest Alabama, where the greatest risk of tornadoes appears to be at this time. Large hail and damaging winds are possible across the entire region. The Storm Prediction Center has placed these areas under a 45% Moderate Risk of severe weather for tomorrow.

Keep up with my weather updates on my Twitter and Facebook page.

Timing

Timing is going to be difficult to pin down tomorrow as some computer models have slowed down the overall movement of the system. Areas near the Delta in Mississippi could see severe weather late tonight, but the remainder of the state shouldn't see any until the morning and afternoon hours. Here in Starkville it'll most likely be after 11am when we begin to see supercells pop up on the radar and the risk for severe weather could extend well into the early evening hours. West Tennessee will likely see the risk for severe weather develop after noon and extend to just after sunset. NWS Jackson's timeline on the left is a pretty good guess at when things will develop and where tomorrow.

Details

The SPC's Moderate Risk verifies quite well on the computer model forecasts. Ahead of a surface low in Missouri tomorrow, surface winds will become southeasterly in East Mississippi and West Alabama while upper-level winds (500mb) will be quite strong out of the southwest. This will cause quite a bit of directional and speed shear from the lower levels to the upper levels of the atmosphere that will aid in the creation of rotating supercell thunderstorms. These individual cells will most definitely carry a tornado risk as they develop and roll through tomorrow after the noon hour. Dew points in the mid to upper 60's will aid in the creation of these storms and send instability (CAPE) values well over 1500 J/kg in places.

The SREF model's Significant Tornado Parameter will be at a 4 for most of Mississippi tomorrow, but again the ingredients for tornado creation will most likely be at their prime in the eastern half of the state in the afternoon. West Tennessee won't be at quite the high level of risk that Northeast Mississippi/Northwest Alabama will be in tomorrow due to a lessening of moisture and instability as you head northward, but tornadoes, wind, and large hail are still in play tomorrow afternoon.

I will be driving from Starkville to Jackson, TN tomorrow afternoon in preparation for my Saturday morning show at WBBJ-TV. I am going to try and time my departure so that I can possibly intercept a supercell from its southern side as I drive northward. Storm motions of over 40 mph and the poor road network in Northeast Mississippi aren't good for storm chasing, so that's off the table unless something extraordinary happens.

4/3 - 5:40pm - Severe Weather Tomorrow Across the South

The Bottom Line

Central/North Mississippi: Severe weather will be possible starting in the late morning hours tomorrow and extend until likely just after 7pm. Supercell thunderstorms could form in front of a main squall line in the early afternoon and produce some tornadoes, but this will be highly dependent on some "iffy" factors like the cap and surface winds. Straight line wind damage, large hail, and some embedded brief tornadoes will be possible with an approaching squall line of storms as we get closer to sunset.

West Tennessee: A squall line of storms will travel from west to east tomorrow between the late morning and middle afternoon hours. This line will strengthen due to daytime heating as it travels eastward, so be especially on the lookout if you live east of Jackson, TN. There's also a possibility for the development of a supercell or two in the southern portions of West Tennessee before the passage of the main line of storms. Straight line winds, hail, a few brief tornadoes, and flash flooding will be possible as the squall line passes through.

Follow me on Twitter or Facebook for updates on tomorrow's severe weather.

Details

Severe weather will be an issue tomorrow around the South as a sharp trough and accompanying cold front advance eastward. The Storm Prediction Center has already put a large portion of the Southeast US under a Slight Risk for severe weather tomorrow, putting particular emphasis on an enhanced severe threat in Mississippi, Alabama, and Tennessee with a 30% outlined area. The SPC's outlook calls for the chance of discrete superecells in front of a main squall line, or QLCS, of storms that could bring damaging winds and some embedded tornadoes.

Here in Mississippi and West Tennessee we'll be watching for a particular area where the most favorable wind shear and instability will come together to create the greatest threat for severe weather. Wind profiles will be most favorable for severe weather as you go northward into Tennessee and Kentucky, but instability will be strongest over Central and North Mississippi as we head into the afternoon hours tomorrow. The meeting of these two "peak" areas of winds and instability will likely be North Mississippi into North Alabama and extreme Southwest Tennessee. The SREF computer model's Significant Tornado Ingredients parameter on the image to the right shows a pretty good estimate of where this area will be during the afternoon tomorrow in the 20 and 30 outlined areas.

To the north of this area straight line winds and brief embedded tornadoes will be the greatest threat as the squall line pushes through during the afternoon. Inside and slightly south of this area is where the best chance for front-running discrete supercells could be. These supercells, should they form, will have a risk of producing tornadoes and large hail. Surface winds from the south or southeast will be needed to produce these tornadoes, so that's certainly something to watch for. Sunlight during the late morning and early afternoon will be the fuel for these supercell storms and the "cap" (warm layer of air above the surface that blocks air parcels from rising and creating thunderstorms) will be crucial. The NAM model indicates that the cap will break and allow for storm development sometime in Central and North Mississippi between 10am and 1pm tomorrow as you'll see on the left. Forecasting when and if a cap will break is extremely tricky, so don't be surprised if we get lucky and supercells don't form due to a stronger than anticipated cap.

Instability in general will be quite adequate tomorrow across Central and North Mississippi as dry air aloft will allow rising moist air parcels from the surface to continue upward, which is the main mechanism for building thunderstorms. The NAM model sounding at 7am tomorrow on the right indicates where this dry air is in relation to the moist air at the surface.

The timing of when the main line of storms will come through has been an issue on some of the computer models. The SREF and NAM models seem to be in agreement that the severe weather threat will begin sometime after 10am in North Mississippi with the potential for front-running supercells and then having the main line of storms come through Northeast Mississippi near the 7pm hour. The GFS has been a little quicker with this, but it seems the last couple of runs have put it more in agreement with the NAM/SREF and the ~7pm timing of the main line coming through Northeast Mississippi.

With the threat of supercells in the early afternoon and the squall line near nightfall, this will be a fairly long event. There isn't one particular parameter that sticks out as being "historic" or much above average for any severe weather event. The significance here is that each of these parameters (instability, shear, moisture, etc) will meet the required criteria for severe weather and converge over a good chunk of Mississippi, extreme Southwest Tennessee, and Alabama. I don't think there will be a large tornado outbreak of any sort, but tornadoes could be possible in both the front-running supercells and main squall line.

Be sure to keep those NOAA weather alert radios in "alert" mode tomorrow if you live within the SPC's 15% or 30% risk areas. Even though this severe weather event will not break any records, it has the potential to affect a large population and cause damage.

5/28 - 4:30pm - A Few More Scattered Storms

I still think we've been doing pretty well with these scattered storms over the past few days. We've only been hit three times and the rain has not lasted long during each hit. The radar isn't too populated with storms at the moment, but there is potential for the formation of some storms this afternoon with unstable air around. A cold front should come through this evening, which could have some storms with it as well.

The passage of this cold front will allow for dry weather on Friday, but there's a potential for severe weather on Saturday. The latest SREF model puts a bit of instability here on Saturday and there will be a cold front coming through as well. It doesn't look very impressive at this point, but 48 hours allows for quite a bit of change in severe weather forecasting.

More scattered storms will be around next week after Tuesday, but I think these will be a bit less dense than what we've seen this week. Severe weather in Tornado Alley looks like it will crank up next week and continue for at least a week or two after that. Perfect timing I'd say!

9 days until storm chasing begins!

2/8 - 11am - Squall Line?

Take a look at what the SPC just issued for Wednesday into Thursday:



At the moment, the SPC is thinking there will be a squall line (thin line of severe storms, usually packing high winds) east of the Mississippi River on Wednesday based on a front coming through with high dewpoints, indicative of a high level of moisture in the air. Instability will remain marginal at best according to the latest SREF, with the highest concentration remaining just to our west during this event. If we stay overcast the whole day on Wednesday, then instability will certainly be low. A sunnier day on Wednesday could spell trouble. A little bit of shear may come into play around here, but I think that will stay in the deep south. Overall, I think we'll see a fast-moving squall line come through here on Wednesday afternoon or evening, but it shouldn't be too bad. The main threat would be wind damage, but really nothing else because the line should be decreasing in intensity as it comes our way.

I know the clouds and showers weren't a great way to start the day, but temperatures will increase a couple more degrees this afternoon and it looks like we will see some sun. Tomorrow is shaping up to be even warmer than I thought, with highs around the area now expected to top out in the mid 60's! The warm air coming up from the Southeast should stick around for Tuesday and Wednesday, but that supply of warm air will get cut off as the cold front comes through on Wednesday night.

My next blog post will be late tomorrow evening... you'll want to check back for that one.

8/5 - 10am - Edouard Lanfall, Rough Night in Chicago

TS Edouard is making landfall this morning, just north of Houston. This is a northward shift from where it was originally plotted to reach land.



This was very close to becoming a weak hurricane, with winds now at 65mph. The lower limit for a hurricane is 73mph. This storm did close some oil platforms, but oil prices have actually dropped over the last day. Looks like supply and demand can overrule a tropical storm.

Last night, a very large and damaging derecho complex of storms hit Chicago and its Northern Indiana suburbs head-0n. Winds were clocked at 70mph in the city. More than 200,000 homes are without power in the area at the moment. It also caused evacuations at O'Hare airport and Wrigley Field. Here's a radar image I snagged last night:



Around here, we're under a SLIGHT risk for severe storms from the SPC both today and tomorrow. Instability for today and tomorrow is higher than previously thought on the SREF model, so we might get a little more than we bargained for. A line of storms is getting ready to come through the metro around an hour from now. This line has no warnings or watches associated with it, and it looks pretty benign on radar. Since these area coming through this morning, one would think that our storm threat for later today would be quashed. True, it will weaken the potential a bit this afternoon, but there's still a pretty good chance we'll see some severe weather later. If we can clear out the clouds later this morning and into the afternoon, you can bet on it.

Tomorrow's threat looks about the same in terms of severity, but I think those storms will be more isolated due to a passing cold front.

These storms this morning will limit our temperatures today, with highs in the lower 90's instead of upper 90's. Humidity will still be an issue, with heat index values in the lower 100's today. Make sure you wear light clothing and drink lots of water! Tomorrow will see a decrease in temperatures, with a high somewhere in the uppper 80's.

8/3 - 10am - Mid-Week Still Looks Rocky

I mentioned yesterday that we could see some severe weather during the middle of this week. After taking a look at the GFS and NAM models this morning, I can certainly say this might happen. The SPC issued a severe weather outlook yesterday with us in the line of fire for Wednesday. While we're still on the fringe, they still think we're in for some rough weather:



The GFS and NAM confirm this risk, so they're not the only ones saying this. This is all caused by a cold front coming through in relation to a trough sinking down into the Plains states. Instability will be fair, with CAPE values from 1500 to 2000 J/KG according to the SREF. I don't think we'll be in a MODERATE risk or anything higher because we're going to be in the zone of development when this happens. The storms will be immature when they reach us, unless that area shifts north and west. I have a feeling these storms will begin as broken cell clusters and then merge into a line as they mature, especially after the models painted something similar. I'll have more on this as the situation evolves.

In the mean time, it's going to be downright hot! We'll see 90 today, with mid 90's expected tomorrow. Tuesday is the near 100 day, with highs expected in the upper 90's. The heat index will soar over 100 on Tuesday, so don't forget to drink lots of water and limit your activity if possible.